Hello. Chris Wragge
Thank you for posting and providing details in the Microsoft Community.
I understand that you are having trouble finding the Microsoft 365 Preview Experience Portal in Excel.
In order to better assist you, could you please share more information:
- May I ask if your Office had a permanent version of Office license installed before?
You can refer to the following steps before getting your accurate information:
- Check the Office version: Make sure you are using the latest version of Office. in Excel, click File -> Account -> Update Options -> Update Now -> to update Office.
- In Excel, click File->Options>Customize Functions>Select Commands not in Ribbon to see if there is an Office Insider, if so, please try to join it after adding it to the right toolbar.

Looking forward to your reply so that we can help you better.
Best regards
InaX-MSFT |Microsoft Community Support Specialist